The Japanese invasion of Burma (December 1941-May 1942) was one of their last major successes on land during the Second World War (outside China), and saw weak British and Indian forces and their Chinese allies forced out of the country in a campaign that lasted six months but that was decided much quicker.

British and Allied Forces

At the start of the campaign the British had two weak divisions available for the defence of Burma. The 1st Burma Division (General Bruce Scott) was posted in the Shan States, to protect against a Japanese advance north-west towards the Burma Road, while the 17th (Black Cat) Division (General Sir John Smyth) was posted in the south-east. In January 1942 this division contained the 16th Indian and 2nd Burma Brigades. General Wavell had overall command, and once the fighting began he appointed his chief of staff, General Tom Hutton, to command the Burma Army.

In late December 1941 General Wavell visited Chiang Kai-Shek in Chungking, and was offered the Chinese 5th and 6th Armies. If the offer had been accepted at that date then the campaign in Burma might have ended very differently, but at that point Wavell was not willing to have Burma saved by Chinese troops, and so only one division was accepted. This irritated Chiang, and made cooperation much harder when the two armies were eventually accepted.

Even as war came closer in the Far East the British didn't think that Burma would be attacked. In theory the colony's eastern border was protected by neutral Thailand, and it was believed that any invasion would thus have to come by sea, and past the British fortress of Singapore.

The British in Burma suffered from a confused and rapidly changing command structure. Until 1937 the defence of Burma had been the responsibility of the Indian Government. From 1937 until September 1939 the Burmese government was in charge. In September 1939 the Chiefs-of-Staff in London took operational control while the Burmese government retained administrative and financial control. In November 1940 operational control was given to the Far East Command in Singapore, while administrative control was split between the War Office and the Burmese government. On 12 December 1941 control was given back to the commander-in-chief in India, but then on 30 December, two weeks after the first Japanese troops had entered the country, control was given to General Wavell's new South-West Pacific Command, ABDA (American British Dutch Australian Command). During the battle for Burma this command was overrun and Wavell returned to India, but retained command of the battle in Burma.

Japanese Forces

The Japanese invasion was carried out by General Shojiro Iida's Fifteenth Army, which initially consisted of 35,000 men in the 33rd and 55th Divisions. During the campaign the 18th and 56th Divisions joined the army, more than doubling the forces available to Iida. Although the Japanese were outnumbered for much of the campaign, they had two key advantages. While most of the British troops were inexperienced (two years into the war most units in Burma had lost many of their more experienced men as they were drawn into the war against Germany, and more were lost in Malaya), the Japanese divisions were battle hardened.

Perhaps more importantly while the British saw the jungle as an impenetrable barrier and were restricted to operating along the few available roads, the Japanese realised that they could move relatively easily through the jungle. Whenever the Japanese ran into a strong British position blocking a road they sent outflanking forces through the jungle to establish a roadblock behind the defenders. At this stage in the war the British tended to concentrate all of their troops on the front line, and so no reserves were available to remove the roadblocks. Instead troops had to be taken out of the fighting line, allowing the Japanese to overwhelm the weakened front line.

The Japanese Plan

The main purpose of the Japanese invasion of Burma was to cut the Burma Road, the one remaining land supply route to China. The key to the invasion of Burma was the Japanese occupation of Thailand, which was followed by the signing of a treaty of friendship on 14 December 1941. On the following day the first Japanese troops entered Burma in the Kra Isthmus, the narrow land bridge that connects the Malaya peninsula to the rest of south-east Asia.

General Shojiro Iida's Fifteenth Army was now able to threaten a huge stretch of the Burmese border. The Japanese plan involved two main thrusts. First the Southern Army would attack the southern tip of Burma and occupy the string of British airfields that connected Burma with Malaya, and then once the invasion of Malaya was well underway Iida would cross the border further north, from Raheng, and advance towards Rangoon. With Rangoon and the southern coast in their hands the Japanaese would then be able to advance north up the main Burmese river valleys.

The Campaign

On 16 January 1942 a Japanese battalion occupied Victoria Point, at the southern tip of Burma, giving them their first airfield inside the country. Tavoy fell on 19 January, isolating the garrison of Mergui, which had to be withdrawn by sea. This gave the Japanese control of three airfields, and allowed them to launch the first air raids on Rangoon. These first air raids ended with a rare Allied victory, as the radar assisted fighter squadrons based around Rangoon inflicted heavy losses on the Japanese, forcing them to abandon daylight raids until the radar was lost.

The main Japanese invasion came from Raheng. Their path was blocked by the 16th Indian Brigade (Brigadier J. K. Jones) at Kawkareik, but this force was quickly swept aside (20-22 January) and forced to retreat west to Moulmein. Smyth and Hutton disagreed on the correct way to deal with the Japanese invasion, Smyth wanted to withdraw to clearer ground behind the Sittang River, where his troops might have been able to use their training, while Hutton (under pressure from Wavell) wanted to fight for every inch of ground.

As army commander Hutton got his way, and Smyth was forced to order a battalion to hold Moulmein. The city still fell, on 31 January, and the battalion only just escaped. Once again Smyth wanted to retreat to the Sittang, and once again Hutton ordered him to hold his ground further east, this time on the Bilin River.

Smyth was finally given permission to retreat across the Sittang on 19 February, and his troops began to cross the river on the night of 21-22 February. On the following morning two Japanese regiments attacked the bridgehead on the eastern bank of the river. Although they were held off all day, early on the following morning Brigadier Noel Hugh-Jones, commander of the 48th (Gurkha) Brigade informed Smyth that he could only hold the bridge for another hour and at 05.30 on the morning of 23 February the bridge was blown. Two thirds of the men of the 17th Division were trapped on the east bank of the river, along with most of their heavy supplies and weapons. Much to Smyth's surprise, once the bridge was blown the Japanese withdrew and began the hunt for an alternative route across the river, allowing most of the trapped men to escape, but the loss of the equipment was disastrous.

In the aftermath of the defeat on the Sittang the British pulled back to Pegu, half way to Rangoon, where the 17th Division was joined by the 7th Armoured Brigade. The 63rd Indian Brigade and three British battalions had also reached Rangoon, but the fall of the city was now almost inevitable.

The disaster at the Sittang came just before a series of changes in the British command structure. Smyth was forced back to India on medical orders, and was replaced as commander of the 17th Indian Division by Brigadier Cowen. On 5 March General Hutton was replaced as commander of the Burma army by General Alexander. At about the same time Wavell's combined ABDA (American British Dutch Australian) command, based on Java, was dissolved after the Japanese conquest of most of its operating area, and Wavell returned to India.

Alexander was nearly trapped in Rangoon. A Japanese division was closing in on the city as he arrived (5 March), but its commander was under orders to sweep around the city to the north and attack from the west. On 7 March, as this division was moving around the city, Alexander realised that he couldn't hope to hold Rangoon, and ordered an evacuation. When the British attempted to leave along the road north to Prome they ran into a Japanese roadblock. A series of attacks on this roadblock failed, and there was a real chance that the entire garrison would be captured, but the Japanese commander, having safely passed to the west of the city, withdrew his roadblock, and the British managed to escape to Prome. On 8 March, as the last British train left Rangoon, the Japanese marched into the undefended city from the west.

After the fall of Rangoon the fighting died down. During the rest of March both sides received reinforcements and prepared for the second phase of the campaign – the inevitable Japanese attack north into the heart of Burma.

On the Allied side General Slim arrived to take command of a newly formed Burcorps, which included the 7th Armoured Brigade, 1st Burma Division and 17ths Indian Division. The British finally accepted the offer of Chinese help, and the 5th and 6th Chinese Armies entered Burma from the north to form the left wing of the new Allied line, giving Alexander and Slim around 165,000 men, 95,000 of them from the two Chinese armies under Stilwell.

The Japanese also received reinforcements – the 18th and 56th Divisions – giving Iida around 85,000 men. Despite their numerical advantage the British and Chinese were now fighting at the end of very long and tenuous supply lines. The loss of Rangoon's radar meant that the Japanese soon had command of the air, so the Allies came under constant air attack.

Serious fighting resumed in late March. The Japanese concentrated three of their four divisions against the two Chinese armies, with the 55th and 18th Divisions advancing in the centre, to Toungoo (30 March) and Mandalay (1 May), while the 56th Division advanced in the east, reaching Lashio (29 April), cutting the Burma Road, the last overland supply route into China. In the west the 33rd Division advanced up the Irrawaddy against the British, forcing them out of Prome (2 April) and Magwe (16 April). On 21 April Alexander ordered a general retreat across the Irrawaddy, and on 26 April the British began their long retreat back to the Indian border.

The retreat came close to turning into a rout, but never quite crossed that line. The presence of the 7th Armoured Brigade played a major part in this – when the Japanese established their roadblocks across the British line of retreat the tanks were able to clear them much more quickly than infantry, making sure that the pace of the retreat never dropped too far. Alexander also played an important role, maintaining a calm atmosphere that helped to maintain order.

It was a badly weakened army that crossed into India in the first half of May, but it was still an army. Despite this it was really the monsoon that saved the army, preventing the Japanese from continuing their pursuit at the same time as it made life a misery for the retreating Allies. When the last British troops crossed into India in mid May it marked the end of a 1,000 mile retreat that had begun in south-east Burma, the longest in British military history.

The British and Burmese lost 13,463 men during the campaign in Burma, while the Chinese may have lost as many as 40,000 men. Japanese losses were much lower, at 4,597 dead and wounded. The battle in the air was a little more equal, with 116 aircraft lost by the Allies and a similar number by the Japanese.